RADIATION THERAPY in pediatric BONE TUMORS Dr M.Tabatabaeefar Radiation oncologist Shahid Beheshty Uni. Imam Hosain Hospital Tehran IRAN

INTRODUCTION Primary bone tumors are rare malignancies. (6 percent of all childhood cancers) Most common amongst them are : Osteosarcoma Ewing’s sarcoma

OSTEOSARCOMAS

Osteosarcomas are highly radio resistant tumors The management basically comprises of surgery and chemotherapy. Standard of care is neo adjuvant chemotherapy followed by limb conserving surgery

Radiotherapy has been reported to improve local control of borderline or unresectable extremity osteosarcoma, vertebral osteosarcoma and pelvic osteosarcoma. It has also been used to treat osteosarcomas of the mandible.

INDICATIONS FOR RT IN OSTEOSARCOMA Definitive : Unresectable disease Patients who refuse surgery/medically inoperable Sites not amenable for surgery : Pelvis vertebral Jaw Margin positive disease after surgery (Close margins after surgery) Palliation

RADIATION THERAPY TECHNIQUES Patient positioning and immobilization : Depends on the site to be treated Immobilization should be done adequately so that the fields are adequately reproducible. The lesion should be positioned such that the entrance and exit of the beam(s) do not expose contralateral limbs or other tissues unnecessarily.

Fields and borders : Dosage : Axial : 2 cms margin Extremity : 4-5 cms margin Strip of skin to be spared to prevent lymphoedema To restrict fields at anatomical barriers Dosage : 60 Gy in 30 # for microscopically involved margins 66 Gy in 33 # for macroscopic disease 70 Gy in 35 # for inoperable disease From initial tumor dimensions on the pre operative imaging

AVAILABLE TECHNIQUES OTHER Techniques : 3D Conformal Radiation therapy IMRT Proton beam therapy OTHER Techniques : Extracorporeal and Intraoperative RT : The extracorporeal technique includes en bloc resection of the tumor and surrounding soft tissues, irradiation of the specimen, and reimplantation, often with the aid of prostheses. In IORT, the operative field is exposed and radiotherapy is administered. No resection of the tumor is performed.

Palliative : Palliative RT for pain management In cases of big lesion causing mass effects Rhenium, Strantium, Samarium 153 Whole lung irradiation : EORTC-20781/SIOP-3 phase 3 trial 240 P to 3 arms: ChT, WLI (20 Gy), ChT & WLI DFS & OS: NO Diff with the recognition of the other advantages of systemic therapy, prophylactic lung irradiation has fallen out of favour.

Ewing sarcoma

history Historically, RT was preferred over surgery because of less acute morbidity, acceptable rates of local control (50 to 77 percent), and poor long-term prognosis, largely due to distant dissemination in the absence of effective chemotherapy

Ewing sarcoma family are a radio sensitive tumor The management basically comprises of surgery and /or RT and chemotherapy. Standard of care is neo adjuvant chemotherapy followed by surgery and /or RT and then chemotherapy.

Contemporary treatment Contemporary treatment guidelines emphasize surgical resection as the local control modality of choice if it is believed that : The lesion can be resected with negative margins, Without excessively morbidity With the expectation of a reasonable functional result

Surgery is preferred for potentially resectable lesions It avoids the risk of secondary radiation-induced sarcomas In the skeletally immature child, resection may be associated with less morbidity than radiation

In many retrospective series, rates of local control and survival are superior after surgery compared to RT alone ,However, larger cooperative group studies have failed to reflect this advantage, and selection bias likely accounts for at least some of these results. Smaller, more favorably situated peripheral tumors are more often resected while larger, axial lesions are referred for RT.

INDICATIONS FOR RT IN Ewing Sarcoma Definitive : Unresectable disease Patients who refuse surgery/medically inoperable OR ,Sites are not amenable for surgery : Pelvis Vertebral Preop RT: marginally resectable tumore Post op RT :Margin positive disease after surgery (Close margins after surgery) Palliation

Definitive RT 12 week VAC/IE then,45Gy to PTV +GTV boost (55.8 Gy to post CHT GTV in responsive and 59.4 Gy in non responsive )

Preop RT 36 to 45 Gy to GTV + 2 cm margin

Post Op RT RT should begin within 60 days of surgery and concurrently with CHT R0 resection : poor CHT response , 45Gy R1 resection : 45 Gy R2 resection : 45Gy +10.8 boost

RT FOR METASTATIC DISEASE Management of the primary site  it may be difficult to justify a large resection of the primary site because of the poor long-term prognosis Start early or late ?

Metastatic disease rt Boost?? Whole lung RT (Post CHT /Metastasectomy) 15 Gy /10 F for patients less than 14 years old 18 Gy /10 F for patients more than 14 years old (current study ,below or above 6 years ,12 vs 15 Gy ) Boost??

CONCLUSIONS TEAM WORK

The role of radiation therapy in the management of bone tumors depends on the histology of the tumor and the resectability. Surgery forms the mainstay of management of most of the tumors of the bone. However, radiation therapy has a significant role to play in inoperable or incompletely excised tumors for adequate local contol.

The newer modalities of delivering radiation therapy and “tailored field” radiation therapy approach has led to significant decrease in the toxicity. The toxicities are also contributed by the chemotherapy used for the treatment of the tumor and cumulative effect of both should be considered while planning a treatment.

SEQUELAE OF TREATMENT Acute effects Desquamation of the skin, myelosuppression, mucositis, diarrhea, nausea, and cystitis. Patients receiving whole lung irradiation are at risk for radiation pneumonitis. Acute reactions are usually self-limited and subside within 10 to 14 days of RT completion

Late effects Arrest of bone growth Soft tissue induration and fibrosis pathologic fractures

arrest of bone growth Younger, prepubertal children are at greatest risk for radiation-induced arrest of bone growth. Sparing of uninvolved epiphyseal plates minimizes limb shortening after RT of extremity lesions.

soft tissue induration and fibrosis RT doses above 60 Gy are associated with markedly increased rates of soft tissue induration and fibrosis   High-dose circumferential irradiation of an extremity is associated with edema, fibrosis, and compromised limb function . This can be avoided by sparing of an adequate strip of tissue

pathologic fractures Weight-bearing bones are at risk for pathologic fractures. The highest risk is within the first 18 months of RT completion.

Second malignancy after RT With protocols utilizing lower doses of RT and tailored RT fields suggest that the magnitude of the risk is somewhat lower.

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